Influence of plate-out oil film on lubrication characteristics in cold rolling

Abstract

Oil-in-water (O/W) emulsions are widely used in tandem cold rolling mills as coolants in order to reduce frictional forces and prevent heat scratches. Although the lubricating properties of O/W emulsions are determined by various factors, two particularly important ones are the amount of plate-out oil on the strip surface and the dynamic concentration mechanics of the emulsion at the inlet of roll bite, which has been a subject of much interest since the 1970s. As many studies have focused only on a single phenomenon, it is important to simulate the interaction of the two phenomena as it occurs in actual cold rolling. In this paper, first, a new method of evaluating the relationship between plate-out oil and lubrication characteristics is proposed, which enables control of plate-out oil before rolling. It was found that rolling force decreased when a plate-out oil film was formed before rolling, but the reduction of rolling force was saturated when the amount of plate-out oil exceeded a certain level. The influence of roughness, the roll coolant, and other factors were also examined using the proposed method. In particular, in tandem cold rolling, it is necessary to consider the influence of plate-out oil carried over by the preceding stand on the lubrication characteristics of the following stand. The results of this research suggest that it is possible to clarify the mechanism of emulsion lubrication using the proposed method. © 2012 ISIJ.